Last updated: May 2026
Find the time between two clock times, add or subtract time durations, or convert a total number of seconds into hours, minutes, and seconds.
Start & End Times
Duration Rows
Convert a Duration
Time duration is the measure of how long an event lasts — the gap between a start point and an end point expressed in days, hours, minutes, and seconds. Calculating elapsed time by hand is tricky because time uses a sexagesimal (base-60) system: 60 seconds make a minute, 60 minutes make an hour, and 24 hours make a day. Unlike decimal arithmetic, you can't just subtract 9:45 from 11:20 as ordinary numbers; you must borrow across boundaries (an hour = 60 minutes, a day = 24 hours). The calculator handles all this automatically, including cases where the end time is on the following day.
Duration calculations appear everywhere: project management (how long did a sprint take?), fitness tracking (how long was a workout?), billing (how many hours to invoice?), cooking (how long has the roast been in?), and travel planning (what is the total flight time with a layover?). Converting the result to a decimal — e.g., 1 hour 45 minutes = 1.75 hours — is essential when multiplying by an hourly rate or entering data into spreadsheets. The conversion is simple: divide the extra minutes by 60 and add to the whole hours.
| Unit | Seconds | Minutes | Hours |
|---|---|---|---|
| 1 Second | 1 | 0.01667 | 0.000278 |
| 1 Minute | 60 | 1 | 0.01667 |
| 1 Hour | 3,600 | 60 | 1 |
| 1 Day | 86,400 | 1,440 | 24 |
| 1 Week | 604,800 | 10,080 | 168 |
| 1 Month (avg) | 2,629,800 | 43,830 | 730.5 |
| 1 Year (365 days) | 31,536,000 | 525,600 | 8,760 |
How do I calculate elapsed time manually?
Convert both times to total minutes from midnight (or from the same reference point), subtract the earlier from the later, then convert back to hours and minutes. For example: 2:30 PM = 870 minutes; 9:45 AM = 585 minutes; 870 − 585 = 285 minutes = 4 hours 45 minutes. For spans crossing midnight, add 1,440 (minutes in a day) to the end time before subtracting.
Can the calculator handle time durations that cross midnight?
Yes. When the end time is earlier in the day than the start time, the calculator automatically assumes the end is on the following day and adds 24 hours accordingly. For example, a start of 11:00 PM and end of 3:00 AM correctly calculates as 4 hours, not a negative duration.
How do I add two time durations together?
Add the hours and minutes separately, then carry over when minutes reach 60. Example: 2 hr 45 min + 1 hr 30 min = 3 hr 75 min = 4 hr 15 min (since 75 − 60 = 15 extra minutes with 1 carried to hours). For seconds: same logic applies at the 60-second boundary. The calculator handles multi-duration addition automatically.
What is the difference between "duration" and "time"?
Time (or a "time of day") refers to a specific point on the clock — 3:00 PM is a moment. Duration refers to a quantity of elapsed time — 3 hours is a span. You subtract two times to get a duration; you add a duration to a time to get a new time. Duration has no AM/PM — "4 hours 30 minutes" is the same regardless of when it starts.
How do I convert hours and minutes to a decimal for billing or spreadsheets?
Divide the minutes by 60 and add to the whole hours. Examples: 2 hours 30 minutes = 2 + (30 ÷ 60) = 2.5 hours. 1 hour 45 minutes = 1.75 hours. 3 hours 20 minutes = 3.333 hours. To go the other direction, take the decimal portion and multiply by 60 to get back to minutes: 0.333 × 60 ≈ 20 minutes.